1. Field of the Invention
The present invention relates to flame-retardant impact-modified battery boxes based on polycarbonate, which contain a silicone-acrylate composite rubber as graft polymer and a phosphorus-containing flame retardant and which have high impact resistance at low temperatures, good flame resistance with low wall thicknesses and excellent chemical resistance. The present invention also relates to the use of the polycarbonate compositions according to the invention to produce battery boxes.
2. Description of Related Art
WO-A 2004/069914 discloses flame-retardant polycarbonate compositions which contain polyalkyl(alkyl)acrylate and halogen-free oligophosphates and are free from polymers whose synthesis involves butadiene, styrene or acrylonitrile. The compositions are characterised by good weld line strength, chemical resistance, heat resistance, ultimate elongation and flowability. The compositions of the present invention differ from the compositions according to WO-A 2004/069914 in that the compositions according to the invention contain no rubber-free polyalkyl(alkyl)acrylate.
WO-A 2002/046305 discloses impact-modified, flame-retardant polycarbonate compositions containing polycarbonate, impact modifier, phosphorus-containing flame retardants. The compositions are characterised by an improved notched impact strength in the low-temperature range. However, WO-A 2002/046305 discloses no compositions containing an impact modifier having a graft base consisting of silicone-acrylate composite rubber.
EP-A 635547 discloses flame-retardant polycarbonate compositions containing polycarbonate, a copolymer gel, an impact modifier based on acrylate or diene rubber, a flame retardant such as for example oligophosphate and optionally an impact modifier having a graft base consisting of diene rubber, acrylate rubber or EPDM rubber. However, EP-A 635547 discloses no compositions containing an impact modifier having a graft base consisting of silicone-acrylate composite rubber.
U.S. Pat. No. 6,423,766 discloses flame-retardant polycarbonate compositions with an impact modifier having a graft base consisting of silicone-acrylate composite rubber, the weight ratio of impact modifier to phosphorus from the phosphate being between 2 and 15. The compositions have improved mechanical properties and good processing characteristics. The compositions according to the present invention differ from the compositions according to U.S. Pat. No. 6,423,766 in that the compositions according to the invention have a higher weight ratio of impact modifier to phosphorus from the phosphate.
However, none of the documents cited describes battery boxes having the properties according to the invention or the use of the compositions according to the invention for the production of battery boxes.